Driving mechanism for power lawn mowers



Aug. 15, 1950 E. s. GEORGE ETAL DRIVING MECHANISM FOR POWER LAWN MOWERS Filed Oct. 25, 1947 Zinnentor 5y vi attorney g5 Patented Aug. 15, 1950 I UNITED STATES PATENT" OFFICE.

DRIVING MECHANISM FDRPOWERLAWNJ WERS Edwin S. George; Bloomfield Hills; and Harold L. Blydenburgh; Highland Park; Mich, assignors to TheMoto-Mower Gompany, Detrit;.Mich., .acorporation of.-Michigan.

Application October 25, 1947', SerialN-o. 782,158

the driving connection between the engine'drive shaft or other power output shaft and the cutting reel rotating mechanism is made or broken by anidler pulley-appliedagainst the inside of the driving belt for tightening or loosening the belt which interconnects these elements, thereby eliminating alternate flexing of the belt and. accordingly decreasing its wear and increasing its life.-

Another object is to provide a power lawnmower'driving mechanism as setforth above wherein an idler pulley is mounted onan arm' which is pivotallymounted upon a portion of the engine crankcase or frame spaced apartfrom the engine drive shaftandmoved to and froxby a rod connected to a hand lever on the lawnmower guiding handle so as to tighten-or loosen the belt by engaging or disengaging: the idlerpulley therewith.

Another object is to provide-a pow-er lawnmower driving mechanism as setforth in the preceding objects wherein the hand lever and rod.

are so mounted and adjustedthat the rod passes slightly over the deadcenter' formedby the hand.

lever pivot when the idler pulley has been moved 1 its maximum distance into engagementwiththe. belt-to tighten it, an adjustment being preferably provided on the rod to shorten or lengthen the distance between the idler pulley axisandthe' pivot. axis of the rod on the hand lever so as:

Figure 2 is a fragmentary top plan view of'the;

end'of the power lawnmower having the driving mechanism shown in Figure 1;

Figure 3is an approximately vertical section along the line 33 in Figure 1, showing details of the belt tightening idler-pulley andarmyand Figure 4 is a vertical section along the. line 4-4 in Figure 1.

Referring to the drawings in detail, Figure 1' shows a small power lawnmower generally designated l0 equipped with. a preferred form:

oi the driving mechanism of the present: inven-e secured. thereto. a-sby the bolts 23.

2. tion, generall rdesignated'lli Only that portion of the power-lawnmower 'illi'iswshown which contains the driving mechanismll adjoining parts, the remainder being conventional andbeyond thescopeof the present invention.

The power lawnmower It] .is provided with the usual frame generally. designated l2 formed byend plates' I 3? (one: only being. shown) interconnected :by tie rods M and a cutter bar 15, the

latter being mounted on arms Idextendingdowmward and rearward from the end plates l3. The; end' plates l3 are also interconnected vby a rod or stationary shaft H; the reduced diameter endslflzof which. pass through the endbosses' i arms 29 extending upwardly andzrearwardly from the end. plates-i2 and are threaded to receive lock-nuts 2] (Figure 2);

The: end plates: .1 3.".are'; provided with axles 22 Ptotatably mounted on theaxles 22 are. wheels 24 carrying tires 25: Journaledin theend plates Iii-are the opposite ends: of a cutting .reelshait' 25 carrying the: usual cutting. reel :21: equipped with spiral cutting; blades 28;; mounted: on conventional spiders (not shown) and aligned with the cutting edgeofsther-stationary cutter bar l5: to cut the grass asthe mowerri fliadvances.

Bolted-as; at 29 to the. ire-melt: is the base 35' of; an internal combustion engine generally designated; 31 cylinder block 32 and crankcase331 in which is journaledrthe engine crankshaft or output shaft 34, the latter being supported at one end by a boss 35 (Figure 2). An apron 36 extends over the-top oi'wthe. frame [2" and conceals the parts beneath as well. as protecting themfrom dust or dirt.

Mounted: on: the engine output shaft 34 and secured theretoas: by the pin .35ais a: driving pulleyBl over which passes .a .belt 38; The latter also encirclesand drives'adriven pulley 39 which has .a hub 40; loosely and rotatably mounted uponthe :shaft. 1 1 (Figure12) i The hub 40 also eatries a sprocket- 41: which is partially encircled by a sprocketrehainfli; the latter also; partially encircling a sprocket; 44 mounted upon the cuttingrreelshaft'Zfi. In this manner, thezcutting reel 2]" is; driven fromthe engine output.

shaft .34 by'means ot the belt .38. In" order to preventithe belt ,SB-irom-looping outward along its'forward' courseand .there-by binding' in either of the pulleys 3lor 39-, theapron-BS-adjacent the belt. Silvia-provided with an. upwardly extending.- U- holtlS se'curedathereto-as by'the. nuts; 45134116..

and its having the usual cylinders or 41 threaded upon the free ends thereof on opposite sides of the apron 36 (Figure 4), the midportion 48 thereof encountering the forward course of the belt 38 when it loops forward.

The driving mechanism H, in addition to the pulleys 31 and 39 and belt 38, also includes an idler pulley 55 (Figures 1 and 3) which engages the inside of the belt 38. The idler pulley 50 is journaled upon a bushing secured by the bolt or stud 52 to the boss 53 upon the lower end of a swinging arm 54, the boss 53 having a threaded bore 55 for receiving the threaded end of the bolt or stud 52. The arm 54 at its upper end carries a boss 55 which is pivotally mounted upon the portion 56 of the stud bolt or pivot bolt 51 (Figure 3), the latter being threaded into the bore 58 in the boss 59 which projects horizontally from the engine crankcase 33.

Threaded into the hole 55 in the intermediate portion of the arm 54 is a stud bolt or pivot bolt 5 I, the portion 52 of which pivotally supports the collar 53. Secured to the collar 63 is one end of an adjustable rod unit 54 consisting of rod sections 55 and 56 having oppositely threaded ends 67 and 58 respectively threaded into the correspondingly oppositel threaded bores 69 and 15 of an adjusting sleeve H (Figure 1). The upper end of the rod section 66 is connected to a collar 12 which pivotally engages a pivot pin 13 mounted on the end of one arm 14 of a bell crank lever 15, the other arm 16 of which serves as a handle. l

The hub of the bell crank lever 15 is journaled upon a pivot pin or stud bolt 71 which in turn is seated in a tubular bracket 18 mounted upon the upper portion of a handle 19 which is provided with a cross bar 83 for the hands of the operator. A pin 81 mounted upon the bracket 18 engages a projection 82 on the bell crank lever 35 and limits its swinging motion in that direction. It will be observed from Figure 1 that when the lever i5 is in the position shown therein, the axis of the rod section 65 passes slightly beyond or over the axis of the pivot stud or bolt ll before the projection 82 hits the pin 8!, the rod section 66 thus passing over dead center and thereby holding the arm 54 and idler pulley 55 in their belt-tightening positions (Figure l). The handle 19 extends downward in yoke portions 83,

the lower ends 84 thereof being flattened (Figure 2) and bored for the passage of the threaded ends of the shaft II.

In the operation of the invention, to cause the engine shaft pulley 31 to drive the sprocket pulley'39 and therefore rotate the cutting reel- 2? so as to cut the grass, the operator grasps the handle portion 16 of the bell crank lever 15 and swings it into the position shown in Figure 1. Assuming that the sleeve H has been rotated a sufficient amount in one direction or the other to shorten or lengthen the rod unit 54 so that the arm 54 is in the most suitable position where the idler pulley 55 engages the inside of the rear-' ward course of the belt 38 to sufficiently tighten the lat er, the belt 38 transmits power from the driving pulley 3'! to the driven pulley 39. The latter in turn rotates the sprocket 4i and this rotates the sprocket 44 by means of the sprocket chain 43, causing the cutting reel shaft 26 and cutting reel 2'! to rotate and cut the grass. At the same time, the lower arm 14 of the bell crank lever 15 swings the axis of the rod section 66 across its dead center consisting of the axis of the pivot or stud bolt ll, the projection 82 coming to rest against 1 the pin 8|. The

operator then grasps the cross bar and pushes the lawnmower forward, causing it to cut the grass and .at the same time guiding it in the desired path.

When the operator desires to halt the rotation of the cutting reel 21, he grasps the handle 16 of the bell crank lever 15 and swings it forward, causing the rod section 55 to swing over dead center. The rod unit 54 then pushes upon the pivot bolt 6| mounted on the swinging arm 54 and swings the latter forward about the pivot bolt 51, carrying with it the idler pulley 50. This causes the belt 38 to slacken, loosening its grip upon the pulleys 31 and 39. The U-bolt 45 acts to engage the forward course of the belt 38 and prevent it from looping outward, thereby also preventing it from resuming its grip upon the pulley 31 and accidentally continue the driving connection.

Since the swinging arm 54 for the idler pulley 50 is journaled upon a stationary element, namely the stud bolt 51, it is subject to negligible wear. In contrast to this, if they arm 54 is mounted upon the engine shaft 34, excessive wear occurs at the pivotal supporting point of the arm, even when anti-friction bearings are used. Since the stud bolt 51 does not rotate, as does the engine shaft 34, anti-friction bearings for this purpose are not needed in order to pivotally support the arm 54 and a simple yet effective driving mechanism is provided. In practice, it is also found that the belt 33 operates satisfactorily as a clutch in this manner, even though the idler pulley 50 tightens it on the tight or rearward side of the belt 38.

Prior belt-tightening mechanisms tighten or loosen the belt by urging an idler pulley inwardly against the outside of the belt. In such prior arrangements, the idler pulley requires the belt to flex inwardly whereas its driving and driven pulleys require it to flex outwardly. This alternate inward and outward flexing in opposite directions of prior mechanisms subjects the belt to great strain and materially shortens its life. In the belt-tightening mechanism of the present invention, however, the idler pulley is applied against the inside of the belt and urges it outwardly. When the belt passes over the idler pulley in the present mechanism, therefore, it not only flexes in the same direction as it does on the driving and driven pulleys but actually reduces the flexing at these pulleys. Consequently, the belt-tightening mechanism of the present invention, by eliminating alternate flexing of the belt in opposite directions and by reducing the amount of flexing in the same direction, namely outward flexing at the driving and driven pulleys, greatly decreases the strain on the belt and materially adds to the life of the belt.

What we claim is:

A driving and clutching device for drivingly connecting the cutting mechanism of a power lawnmower to the output shaft of a driving engine, comprising a driving wheel connected to said output shaft, a driven wheel connected to said cutting mechanism, an endless flexible connector loosely interconnecting and partially encircling said wheels, a pivot member mounted on a portion of said lawnmower outside said flexible connector and spaced apart from said output shaft, a lever pivotally mounted on said pivot member, a pressure wheel rotatably mounted on said lever remote from said pivot member and disposed inside said flexible connector and swingable as a unit with said lever into tightening engagement with the inside surface of said flexible connector, and an operating device operatively connected to said lever for swinging said lever to and fro relatively to the inside surface of said flexible connector. 5 EDWIN S. GEORGE. HAROLD L. BLYDENBURGH.

REFERENCES CITED The following references are of record in the 10 file of this patent:

Number 6 UNITED STATES PATENTS Name Date Stegeman et a1. Aug. 18, 1931 Herge Oct. 18, 1938 Cooper May 30, 1939 Moyer Aug. 11, 1942 

